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<head><meta charset="utf-8"><title>LTO passes in profile output · t-compiler/help · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/index.html">t-compiler/help</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/LTO.20passes.20in.20profile.20output.html">LTO passes in profile output</a></h3>

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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/LTO%20passes%20in%20profile%20output/near/183212976" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> gizmondo <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/LTO.20passes.20in.20profile.20output.html#183212976">(Dec 11 2019 at 23:23)</a>:</h4>
<p>Hi,<br>
I've been wondering why "-Z time-passes" can show "LTO passes" lines even when LTO is not enabled? It's disabled by default, right?<br>
I've seen them here - <a href="https://wiki.alopex.li/WhereRustcSpendsItsTime" target="_blank" title="https://wiki.alopex.li/WhereRustcSpendsItsTime">https://wiki.alopex.li/WhereRustcSpendsItsTime</a>. And I'm seeing lots of them on a toy program where they even take significant time (~25% if I interpret the results correctly). <br>
Any ideas?</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/182449-t-compiler/help/topic/LTO%20passes%20in%20profile%20output/near/183485894" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> gizmondo <a href="https://rust-lang.github.io/zulip_archive/stream/182449-t-compiler/help/topic/LTO.20passes.20in.20profile.20output.html#183485894">(Dec 15 2019 at 12:10)</a>:</h4>
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<p>It's disabled by default, right?</p>
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<p>Ok, I was wrong here, some LTO is performed by default in optimized builds when number of codegen units &gt; 1.</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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